Comparison of different antibody preparations against pregnancy‐associated plasma protein‐A (PAPP‐A) for use in localization and immunoassay studies

Abstract
Summary. Four antibody preparations against pregnancy‐associated plasma protein (PAPP‐A) were compared in order to find an explanation for the contradictory results published on tissue localization, clinical usefulness and biological function of PAPP‐A. One of the preparations studied was a rabbit anti‐PAPP‐A antiserum which has been offered for general scientific use (Bischof et al. 1979). Only the IgG fraction of anti‐PAPP‐A antisera which appeared to be monospecific and had been further absorbed with fetal connective tissue gave specific uniform staining of the cytoplasm of the syncytiotrophoblast exclusively. Circulating PAPP‐A could not be detected by RIA employing this IgG preparation in the non‐pregnant state, or before 18 days after conception. Circulating PAPP‐A could be detected in all seven pregnant women studied within 4 weeks after conception. Identical results were obtained with a commercially available IgG fraction against PAPP‐A.

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